Non-stick photoresist laminate

ABSTRACT

A photoresist laminate includes a substrate (such as PET film having a thickness of between about 0.002-0.003 inches) with first and second faces, a first film layer, and a second layer. The first film layer is a photoresist material (radiation sensitive) which is soluble or dispersible in water but which will harden upon sufficient exposure to radiation so as to become substantially insoluble or non-dispersible. The first film layer may be of any conventional photoresist material (e.g. having a thickness of about 0.002-0.009 inches) and is operatively disposed on the substrate first face (either directly connecting it or connected to a membrane support layer which in turn is directly connected to the substrate first face). The second layer is of a material and thickness so that it substantially prevents sticking of the first film layer to other surfaces, while not significantly interfering with the radiation sensitivity thereof. The second layer is on the opposite side of the first film layer from the substrate, and may comprise a mixture of polyvinyl alcohol solution and polyvinyl acetate emulsion, having a thickness of less than 0.0005 inches (e.g. about 0.0001-0.0002 inches). The laminate is used in a method of making a stencil for abrading or etching by exposing the laminate to radiation, processing a laminate by spraying water on the laminate to remove the soluble or dispersible portion, and then using the stencil so formed as a mask on the surface of an object to etch or abrade the surface.

BACKGROUND AND SUMMARY OF THE INVENTION

Products that have decorative patterns formed on the surface of theproducts by abrasion (typically sandblasting) or etching are becomingincreasingly more popular. A wide variety of techniques have beendeveloped to effectively produce masks to facilitate accurate productionof such objects, such as shown in U.S. Pat. Nos. 5,370,762, 4,764,449,and 5,427,890 (the disclosures of which are hereby incorporated byreference herein), and various automated equipment has been developed tofacilitate processing during production of such masks (such as shown inU.S. Pat. No. 5,366,584). The basic processes utilize a photoresistlaminate which may have a variety of constructions, but includes asubstrate and an outer layer of photoresist material (radiationsensitive material which is soluble or dispersible in water but willharden upon sufficient exposure to radiation so as to becomesubstantially insoluble or non-dispersible) facing outwardly from thesubstrate. The photoresist laminate is typically provided in roll formwhere the radiation sensitive material of one part of the roll contactsa substrate on another part of the roll; or the laminate may be providedin sheet form with one sheet stacked upon another with the radiationsensitive material of one sheet contacting the substrate of another.Under some circumstances, especially where there is high humidity orproducts have been maintained in a roll or stacked configuration for along period of time, a problem of sticking may occur. That is, thephotoresist material sticks to the substrate of an engaged part of theroll, or of another sheet. This can be a significant problem sincesticking may cause the photoresist material to be removed or separatedfrom the substrate, and make it unusable for its intended purpose.

Another problem can occur when the photoresist is exposed to UVradiation. The pattern that creates the latent image is printed on apaper vellum or plastic film. This pattern is pressed onto the surfaceof the photoresist during its exposure to radiation. A stickyphotoresist material can cause paper vellums to tear or pull off the inkthat creates the pattern. The sticking can also cause delaminationbetween the photoresist and the substrate film when the vellum isremoved.

In order to overcome this problem, various types of substrates have beenattempted to be utilized, with less than optimum success in preventingor minimizing the sticking problem. Also providing a release liner ontop of the radiation sensitive material (photoresist material) which isremoved prior to use significantly increases the costs of the laminate,makes the laminate bulkier to ship, and introduces another step for theutilization thereof.

According to the present invention a photoresist laminate, a stencilmade therefrom and a method of utilization thereof for abrading oretching, are provided which substantially eliminate or minimize thesticking problem in a simple and effective manner, without significantlyincreasing the cost of the laminate, and without introducing anotherstep for utilization thereof. According to the present invention, duringmanufacture the radiation sensitive material is provided with a verythin coating which is readily removed during processing, and does notsignificantly interfere with the radiation sensitivity of thephotoresist material, yet it substantially prevents sticking of thephotoresist material to a substrate of an adjacent portion of thelaminate in a roll, or of another sheet in the stack, or even to othermaterials that the photoresist material may inadvertently come intocontact with.

According to one aspect of the present invention a photoresist resistlaminate is provided comprising the following components: A substratehaving first and second faces. A first film layer of radiation sensitivematerial which is soluble or dispersible in water but will harden uponsufficient exposure to radiation so as to become substantially insolubleof non-dispersible, and operatively disposed on the substrate firstface. And a second layer of a material and thickness so that itsubstantially prevents or minimizes sticking of the first film layerwhile not significantly interfering with the radiation sensitivitythereof. The second layer is on the opposite side of the first filmlayer from the substrate.

The photoresist laminate may comprise other layers and constructions.For example, a membrane support layer may be provided between thesubstrate and the first film layer and engaging both the substrate andthe first film layer. Also, or alternatively, the first film layer maycomprise two clearly different colored portions, one atop the other,specifically as described in said copending application Ser. No.09/137,702; and the laminate may consist of the recited elements above.

Typically, the second layer has a maximum thickness of about 0.0005inches, e.g. about 0.0003 inches, and most desirably between0.0001-0.0002 inches. While any material suitable for performing thenon-stick, yet not interfering with the radiation sensitivity, functionsmay be provided, one particularly desirable material for forming thesecond film layer comprises a mixture of polyvinyl alcohol solution andpolyvinyl acetate emulsion. The range may be 2-98% by weight of one and98-2% of the other. If a water soluble formula is desired so as tofacilitate wash-away of the second layer during processing, preferablyabout 80%-98% by weight polyvinyl alcohol solution with the remainderpolyvinyl acetate solution (and perhaps some inert materials isprovided). If a substantially water insoluble formulation is desired itcomprises about 80-98% by weight polyvinyl acetate solution with theremainder polyvinyl alcohol solution (and perhaps inert ingredients).

The second layer may he applied in a conventional coating process (e.g.direct roll coating) after the rest of the laminate has been formed, ormay be provided by spraying a fine spray of the second layer material onthe first layer, to form a fine film, using conventional aerosolequipment.

A variety of thicknesses and materials may be utilized. For example thefirst film layer may have a thickness of between about 0.002-0.009inches may be a conventional photoresist material such as described insaid copending application Ser. No. 09/137,702, or a positive or anegative acting film such as described in U.S. Pat. No. 4,764,449, or ofany other conventional construction such as shown in U.S. Pat. No.5,427,890. The substrate typically has a thickness of about 0.002-0.003inches and may comprise PET film, or Mylar® polyester film (e.g. typeS-200 gauge), or any other conventional substrate. The membrane supportlayer, when utilized, may have a thickness of between 3-5 microns andalso may comprise any suitable conventional material. Other layers arealso possible depending upon the particular use or circumstances, againsuch as described in U.S. Pat. No. 4,764,449.

The laminate may be in a roll form with the second layer contacting thesecond face of the substrate in a substantially non-stick manner.Alternatively, the laminate may be in sheet form, and stacked with othersubstantially identical laminates so that the second layer of one sheetengages the second face of the substrate of another sheet.

The laminate as described above preferably is utilized in a method ofmaking a stencil and ultimately an etched or abraded object, such asdescribed in either the inventive or background portions of copendingapplication Ser. No. 09/173,702. For example, by utilizing the laminateas described above a method of making a stencil for abrading or etchingusing a negative acting or positive acting photo-resist laminate asdescribed above, is provided comprising: (a) Exposing the laminate and apattern to radiation to cause hardening of some portions to define thepattern as a latent image in the photoresist first film layer byproviding some portions that are soluble or dispersible in water, andother portions that are substantially insoluble or non-dispersible (b)Processing the laminate from (a) by spraying water on the laminate toremove the soluble or dispersible portions of the first layer, and atleast those portions of the second layer covering the soluble ordispersible portions of the first layer, but not the substantiallyinsoluble or non-dispersible patterns of the first layer to ultimatelyproduce a stencil. And (c) using the stencil from (b) as a mask on thesurface of an object to etch or abrade the surface of the object wherethe photoresist film has been removed to form a surface texture in theobject that stimulates the latent image.

Where the first layer comprises first and second clearly differentcolored portions, one atop of the other, then (b) is practiced to firstremove substantially all of the soluble or dispersible portions of thefirst color, and only then to carefully start to remove the soluble ordispersible portions of the second color. The invention also relates toa stencil produced by practicing (a) and (b) of the method as describedabove.

It is the primary object of the present invention to provide aphotoresist laminate which substantially eliminates or minimizes thesticking problem present in conventional photoresist laminates, in asimple and cost effective manner, which does not require changes in themethod of utilization thereof to produce a stencil for masking andultimately producing an etched or abraded object. This and other objectsof the invention will become clear from an inspection of the detaileddescription of the invention and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side enlarged cross sectional view, with the relativethicknesses of the components exaggerated for clarity of illustration,of one embodiment of a photoresist laminate according to the presentinvention;

FIG. 2 is a view like that of FIG. 1 for another embodiment of alaminate according to the present invention;

FIG. 3 is a schematic perspective view of the laminate of the FIGS. 1and 2 in a roll configuration; and

FIG. 4 is a schematic side exploded view of the laminate of FIGS. 1 and2 during stacking, wherein one sheet of laminate will be brought intocontact with another in a stack.

DETAILED DESCRIPTION OF THE DRAWINGS

One embodiment of an exemplary photoresist laminate provided accordingto the present invention is illustrated generally at 10 in FIG. 1. Itincludes a substrate 11 having a first face 12 and a second face 13. Thesubstrate (also often referred to as a support carrier) 11 may be of anysuitable material and any suitable thickness. For example, the substrate11 may comprise PET film of a thickness of between about 0.002-0.003inches. Other materials that may be utilized include BOPP, and Mylar®polyester film (such as type S-200 gauge available from du Pont) witheither a clear unmatted surface or a matte surface, etc.

The laminate 10 further comprises a first film layer 14. The layer 14may comprise a plurality of layers made by coating first one layer andthen another, or may comprise a single layer. Regardless of how the filmlayer 14 is constructed, it preferably typically has a thickness ofbetween about 0.002-0.009 inches, and is a photoresist material, thatis, it is a radiation sensitive (either positive or negative acting)material which is soluble or dispersible in water but will harden uponsufficient exposure to radiation (e.g. UV) so as to become substantiallyinsoluble or non-dispersible. The first film layer 14 is provided sothat it is operatively disposed on the first face 12 of the substrate11. By “operatively disposed” is meant that either the first film layer14 actually contacts and is adhered to the first face 12, or there areone or more intermediate layers which provide effective attachment ofthe first film layer 14 to the first face 12. The radiation sensitivematerial forming the first film layer 14 may comprise any suitableconventional material which performs a function such as disclosed inU.S. application Ser. No. 09/137,702, U.S. Pat. No. 4,674,449, or U.S.Pat. No. 5,427,890.

According to the invention, the laminate 10 also comprises a secondlayer 15 of a material and thickness so that it substantially preventssticking of the first film layer 14 while not significantly interferingwith the radiation sensitivity thereof. The second layer 15 is adheredto the first film layer 14 during use. If a water soluble formula isused, the second layer 15 is adhered to the first film layer 14 untilthe washout process that occurs after radiation exposure. Duringwashout, layer 15 is dissolved away. If a water insoluble formula isused then layer 15 prematurely remains in contact to layer 14. Sincelayer 15 is the layer that will be glued to the article being blasted,it never is contacted with the etching abrasive and therefore will notdisintegrate during use.

Typically the second layer 15 has a maximum thickness of about 0.0003inches, depending upon the material of which it is made. While anymaterial may be utilized for the second layer 15 that substantiallyprevents or minimizes sticking of the first film layer 14 to any otherobject or material (such as to the second face 13 of the substrate 11 ofanother laminate 10, or another portion of the laminate 10) while notsignificantly interfering with the radiation sensitivity of the firstfilm layer 14, one particularly suitable material that may be utilizedas the second layer 15 is a mixture of polyvinyl alcohol solution andpolyvinyl acetate emulsion. The range may be 2-98% by weight of one and98-2% of the other. If a water soluble formula is desired so as tofacilitate washaway of the second layer during processing, preferablyabout 80%-98% by weight polyvinyl alcohol solution with the remainderpolyvinyl acetate solution (and perhaps some inert materials isprovided). If a substantially water insoluble formulation is desired itcomprises about 80-98% by weight polyvinyl acetate solution with theremainder polyvinyl alcohol solution (and perhaps inert ingredients).One particular polyvinyl alcohol solution that may be utilized is AIRVOL540, and one particular polyvinyl acetate emulsion is VINAC XX-240, bothavailable from Air Products and Chemicals, Inc.

The second layer 15 is typically applied with a thickness of betweenabout 0.0001-0.0002 inches, and may be applied by any conventionaltechnique such as utilizing conventional direct roll coating processes,spraying, or the like. Because the second layer 15 is so thin, and issubstantially radiation transparent, it cost effectively substantiallyeliminates or minimizes the sticking problem while not introducinganother step for the utilization of the laminate 10, and while allowingnormal utilization thereof to etch or abrade an object.

The laminate 10 may consist essentially of the substrate 11, first filmlayer 14, and second layer 15 or may comprise a wide variety of otherlayers for performing different functions. Another embodiment whichincludes an additional layer is illustrated schematically at 10′ in FIG.2. In FIG. 2 components comparable to those in FIG. 1 are shown by thesame reference numeral.

In FIG. 2, the laminate 10′ is shown with a membrane support layer 17,for example having a thickness of between about 3-5 microns and of anysuitable material which would adhere to both the first surface 12 of thesubstrate 11 and the first film layer 14, is provided to operativelyadhere the first film layer 14 to the substrate 11. The laminate 10′ mayconsist essentially of the elements 1, 17, 14, and 15, or may comprisestill further layers.

The laminate 10, 10′ is illustrated schematically at 19 in FIG. 3 inroll form, with a corner of the leading edge 20 of the roll 19 curledback so as to clearly illustrate that the second layer 15 of one portionof the laminate 10, 10′; and the roll 19 engages the second face 13 ofthe substrate 11 of another portion of the roll 19, in a substantiallynon-stick manner which will allow utilization of the roll 19 even ifstored for a relatively long period of time, and even in humidconditions.

FIG. 4 schematically illustrates a stack 22 of laminates 10, 10′ in theform of sheets 23. While FIG. 4 shows the sheets 23 separated from eachother, that is simply for clarity of illustration; in use the sheets 23will engage each other stacked one above the other with the second layer15 of one sheet engaging a second face 13 of the substrate 11 of anoverlying or underlying sheet 23.

As described in copending application Ser. No. 09/137,702, the firstfilm layer 14 may comprise two different clearly colored portions oneatop of the other which may be removed (after exposure to UV radiationor the like) in the manner described in said copending application Ser.No. 09/137,702, or the laminates 10, 10′ may be otherwise utilized in amethod for making a stencil for abrading or etching using a negativeacting or positive acting photoresist laminate 10, 10′. Typically thelaminate 10, 10′ is utilized by exposing the laminate 10, 10′ in aconventional pattern to radiation (e.g. UV radiation) to cause hardeningof some portions to define the pattern as a latent image in thephotoresist film layer 14 by providing some portions that are soluble ordispersible in water, and other portions that are substantiallyinsoluble or non-dispersible. The second layer 15 is of a thickness andmaterial so that it does not significantly interfere with the passage ofthe effective radiation (e.g. UV) into contact with the first film layer14, nor interfere with the formation of the latent image therein.

The method is continued by processing the laminate after exposure toradiation, as described above, by spraying water on the laminate toremove the soluble or dispersible portions of the first layer 14 and atleast those portions of the second layer 15 covering the soluble ordispersible portions of the first layer 14, but not the substantiallyinsoluble or non-dispersible portions of the first layer 14, toultimately produce a stencil. Typically because of the thinness of thematerial of which the second layer 15 is formed, it will be completelyremoved during the spraying process, particularly if of a water solublecomposition.

It will thus be seen that according to the present invention aphotoresist laminate is provided, as well as a method of utilizationthereof, and a stencil formed therefrom, which substantially eliminatesor minimizes the sticking problem of the photoresist material that isinherent in conventional laminates. It does so in a manner that does notrequire a separate removable sheet, and does not complicate the methodof utilization of the laminate, and in a cost effective manner.

While the invention has been herein shown and described in what ispresently conceived to be the most practical and preferred embodimentthereof it will be apparent to those of ordinary skill in the art thatmay modifications may be made thereof within the scope of the invention,which scope is to be accorded the broadest interpretation of theappended claims so as to encompass all equivalent products andprocedures.

What is claimed is:
 1. A photoresist laminate comprising: a substratehaving first and second faces; a first film layer of radiation sensitivematerial which is soluble or dispersible in water but will harden uponsufficient exposure to radiation so a to become substantially insolubleor non-dispersible, and operatively disposed on said substrate firstface; a second layer of a material and thickness so that itsubstantially prevents or minimizes sticking of said first film layer toother photoresist laminates while not significantly interfering with theradiation sensitivity thereof; said second layer on the opposite side ofsaid first film layer from said substrate; a membrane support layerbetween and adhering to said substrate and said first film layer andengaging both said substrate and said first film layer; and wherein saidfirst film layer has a thickness of about 0.002-0.009 inches, saidsubstrate has a thickness of about 0.002-0.003 inches, and said secondlayer has a thickness of about 0.0001-0.0002 0.0005 inches.
 2. Aphotoresist laminate as recited in claim 1 wherein said second layercomprises a mixture of about 80-98% by weight polyvinyl alcohol solutionand about 20-2% by weight polyvinyl acetate emulsion.
 3. A photoresistlaminate as recited in claim 1 wherein said laminate is in sheet form,and stacked with other substantially identical laminates so that saidsecond layer of one sheet engages said second face of said substrate ofanother sheet.
 4. A photoresist laminate as recited in claim 1 whereinsaid first film layer comprises two clearly different color portions oneatop the other.